Combined Water Extractor and Electricity Generator

ABSTRACT

A water extraction system having a cooling system adapted to cool air to below the dew point, the cooling system including an absorption chiller ( 1.002 ) including a heat source ( 1.004 ), the system includes an air/heat transfer fluid heat exchanger ( 1.016 ), and a water collector ( 1.022 ) arranged to collect water from the air/heat transfer fluid heat exchanger. The air/heat transfer fluid heat exchanger ( 1.016 ) is adapted to cool the air below the dew point. The chiller can include a heat input in the form of exhaust gasses from a gas turbine. The gas turbine can also drive an electrical generator. The air outlet from the water generator can be used in an air conditioning system. The system can include one or more chillers powered by, for example, turbine exhaust. Additional heat source, such as natural gas can be provided to bring the chillers to the operating temperature. A controller controls the change-over between heat sources.

FIELD OF THE INVENTION

This invention relates to improvements in the use of absorption chillersfor the production of a cooled air or liquid outlet for use inapplications requiring a chilled fluid, such as air conditioning,atmospheric water extraction, and the like.

Our copending Australian patent application AU2008237617 discloses anabsorption chiller water extraction system powered by gas.

This invention builds on that invention to provide a source of chilledfluid for various applications.

BACKGROUND OF THE INVENTION

Air conditioning systems sometimes produce water as a waste product inhigher humidity conditions, but such equipment is not specificallyadapted to the production of water at lower humidity levels because thesystem does not consistently cool the air below the dew point at lowerhumidity levels. For example, an air conditioner may typically cool theroom temperature to a steady state temperature of about 22° C., whilethe dew point can be several degrees less, so that, where the dew pointis below the operating temperature of the air conditioning system, thesystem will not produce useful quantities of water.

Conventional vapour compression air conditioning systems for largebuildings use a water evaporative cooling system to cool the hot heattransfer fluid from the air conditioning heat exchanger after the vapourhas been compressed. In a city of 4 million people, this can result inthe evaporation of the order of 30 mL of water per day.

Absorption chillers use the strong affinity between water and lithiumbromide in the working fluid cycle. An absorption chiller includes asolution pump, a generator, a condenser, an evaporator, and an absorberin a vacuum process.

A dilute solution of lithium bromide solution is collected in theabsorber and pumped to a first heat exchanger where it is pre-heated.

In a second heat exchanger, the solution is boiled by a heat source,such as steam. The vapour is delivered to the condenser. A concentratedlithium bromide solution is left behind. The concentrated lithiumbromide solution is then cooled in the heat exchanger by the weaksolution pumped up to the generator.

The condenser includes an enclosed bundle of tubes. The refrigerantvapour passes through mist eliminators to the condenser tube bundle andcondenses on the tubes. The heat is removed by the cooling water whichmoves through the inside of the tubes. The condensed refrigerant fallsinto a trough at the bottom of the condenser.

In the evaporator the hygroscopic interaction of the lithium bromide andwater creates an effective vacuum. As the refrigerant liquid cools theevaporator tube bundle, the refrigerant liquid boils at approximately 4°C. The latent heat of vapourization causes a cooling effect.

In the absorber the concentrated lithium bromide solution from thegenerator is applied to the absorber tube bundle, and absorbs therefrigerant vapour into solution, creating the vacuum in the evaporator.The cooling water removes the heat generated by the absorption.

The newly diluted lithium bromide solution returns to the solution pumpfor recirculation.

There are various sources of thermal energy. Coal gas and natural gascan be burned to produce heat. Gas turbine electricity generatorsproduce a large amount of waste heat in their exhaust gasses whiledelivering useful electrical energy.

Thus both air conditioning systems and gas turbines produce waste heat,and air conditioning systems also consume water by way of evaporativecooling.

Atmospheric water generators are known which use the vapour compressordriven refrigeration cycle system to cool air below the dew point. U.S.Pat. No. 5,259,203 describes such a system. U.S. Pat. No. 4,255,937describes an electrically operated dehumidifier using standardrefrigeration techniques which serves as a small scale water extractor.U.S. Pat. No. 5,857,344 describes a compressor driven refrigerationsystem used in a small scale water extractor. U.S. Pat. No. 6,705,104also describes a compressor operated refrigeration system used toextract water from air. However, such systems use a large amount ofelectrical energy per litre of water extracted, and are generally notsuitable for large scale water production plants.

It is desirable to provide a cooling source capable of scaling up forindustrial applications.

It is desirable to provide a large scale water extraction system.

It is also desirable to provide a water extraction system which produceswater at an economic cost.

Absorption chillers can use the properties of fluids, such as the latentheat of vaporization, to provide a cyclical endothermic or heatabsorbing process. Energy can be input to the system using an energysource, such as electricity. One such system uses ammonia, hydrogen andwater as the working fluids. A description of such a system can be foundat http://www.gasrefrigerators.com/howitworks.htm

The mixed hydrogen vapour is then separated by using water to absorb theammonia. The heat input is then used to separate the water and ammoniaby evaporating the ammonia.

An alternative absorption chiller system uses a Li/Br salt solution toabsorb water from the air.

Any reference herein to known prior art does not, unless the contraryindication appears, constitute an admission that such prior art iscommonly known by those skilled in the art to which the inventionrelates, at the priority date of this application.

SUMMARY OF THE INVENTION

This invention utilizes latent synergies between exothermal energysources, such as gas turbine generators, internal combustion engines, orcombustible gas supplies, and absorption chillers, condensation watergenerators, and air conditioning systems to produce a tri-generationsystem with good energy efficiency.

The invention provides a water extraction system having a cooling systemadapted to cool air to below the dew point, the cooling system includinga refrigeration system and a heat exchanger, a collector to collectwater, and a gas turbine, wherein the cooling system is an absorptionchiller, and wherein the exhaust gasses from the turbine are used tosupply heat energy to the chiller.

The chiller can additionally or alternatively be powered by electricityor solar energy from a solar collector.

The system can include air flow generator adapted to cause air to flowthrough the heat exchanger.

The air flow generator can be controllable to control the air flowthrough the heat exchanger.

The heat exchanger can include a coolant pipe and cooling fins thermallyconnected to the coolant pipe, wherein the surface area of the fins isenlarged to increase the contact between the air flow and the fins.

The system can include a dew point sensor to determine the dew point ofthe air.

The system can include a controller controlling the air flow generatorto maintain the temperature of the air from the heat exchanger below thedew point.

The invention also provides a combined electricity generation system,air-conditioning system, and water generator, including a turbine drivenelectricity generator, a chiller supplied with heat from the exhaust ofthe turbine, the chiller being connected to an air heat exchanger andcooling the air below the dew point to produce water from condensation,and an air conditioning system receiving cooled air from the outlet ofthe air heat exchanger.

The invention also provides a water extraction system as described inAustralian patent application AU2008237617, including an air intakearrangement adapted to draw air from a source of enhanced humidity air.

The source of enhanced humidity can be the outlet of an evaporatingcooling system.

The invention also provides an absorption chiller system including oneor more absorption chillers, each chiller having at least a first and asecond heat input, the system including a controller, wherein, onstart-up of the chiller, the controller is adapted to turn the firstheat source on to bring the chiller to a first predeterminedtemperature, and wherein controller is adapted to turn the second heatsource on and to turn the first heat source off when the correspondingchiller reaches the predetermined temperature.

The controller can be adapted to bring each chiller to the predeterminedtemperature in sequence.

The invention also provides a method of extraction water from air, themethod including using an absorption chiller to cool an air/heattransfer fluid heat exchanger to a temperature below the dew point, andcollecting water from the air/heat transfer fluid heat exchanger.

The method can include the step of using gas as a source of heat energyto operate the chiller.

The method can use the step of using solar energy as a source of heat tooperate the chiller.

The system can be used to produce potable water by the addition ofsuitable filtration and other water treatment processes as required bythe nature of the water generated from the water extraction system.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment or embodiments of the present invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic illustration of a water extraction systemaccording to a first embodiment of the invention.

FIG. 2 is a schematic illustration of a water extraction systemaccording to a second embodiment of the invention.

FIG. 3 schematically illustrates an absorption chiller suitable for usein relation to the present invention.

FIG. 4 schematically illustrates a further arrangement embodying theinvention.

FIG. 5 is a schematic functional block diagram of a system embodying theinvention.

FIG. 6 is a functional block diagram of the water extraction systemwhich forms part of the system of FIG. 5.

FIG. 7 illustrates a controller adapted for use in an embodiment of theinvention.

FIG. 8 schematically illustrates an embodiment of the invention in whichthe air intake of the water generator system is drawn from the outlet ofan evaporating cooler apparatus.

FIG. 9 is a schematic illustration of a multi-function electricitygenerator, air-conditioner, and condensing water generator.

FIG. 10 schematically illustrates a system combining the features of theembodiments of FIGS. 8 & 9.

FIG. 11 is a photo-superposition of a system according to an embodimentof the invention.

FIG. 12 illustrates a multi-turbine version of a system according to anembodiment of the invention.

FIG. 13 is a flow diagram illustrating a start-up process according toan embodiment of the invention.

FIG. 14 illustrates a general purpose chiller arrangement according toan embodiment of the invention.

FIG. 15 illustrates a system according to a further embodiment of theinvention which uses a gas turbine electric generator to power anelectric chiller.

The numbering convention used in the drawings is nn.nnn, or n.nnn, wherethe digits before the stop indicate the drawing number, and the digitsafter the stop indicate the item number. Where possible, the same itemnumber is used in different figures to indicate the corresponding item.

It is understood that, unless indicated otherwise, the drawings areintended to be illustrative rather than exact representations, and arenot necessarily drawn to scale. The orientation of the drawings ischosen to illustrate the features of the objects shown, and does notnecessarily represent the orientation of the objects in use.

DETAILED DESCRIPTION OF THE EMBODIMENT OR EMBODIMENTS

FIG. 1 shows a water extraction system according to a first embodimentof the invention.

An absorption chiller 1.002, a heat energy input 1.004, a heat transferoutlet pipe 1.006, a heat transfer fluid return pipe 1.008, a heattransfer fluid compressor 1.003, a fan 1.010, fan motor 1.012, air duct1.014, a restrictor valve 1.015, an evaporator/heat exchanger 1.016having fins 1.018 and heat transfer fluid pipe 1.020. The air paththrough the heat exchanger 1.016 emerges in cowling 1.024 located overwater trough 1.022. A temperature sensor 1.026 senses the temperature atthe outlet of the chiller. The sensor 1.026 is connected to a controller1.028. The controller is connected to control the speed of the air flowby controlling the speed of the fan. The controller can also control theheat input 1.004.

The fans and pumps can be powered by electricity from the mains or froma solar generator or other source of electrical power. In oneembodiment, electrical power can be used as an alternative power sourceto operate the chiller.

Further, a system can be provided having two or more power sources. Forexample, the system can include both gas power and electrical power forthe chiller, with a programmable changeover based on the comparativetariffs or energy costs. The energy costs take account of the relativeefficiencies of the gas and electrical systems. Thus the switchover canbe based on the energy cost of electricity divided by the efficiency ofthe electrical chiller compared with the energy cost of gas divided bythe gas efficiency. Thus, if the electrical cost is less than gas duringan off-peak electrical supply period, the system can switch toelectricity. To implement this facility, the system is provided withcontinually updated information on electricity tariffs, as well as withthe cost of fuel for the turbine. The electricity tariff can be providedby an internet link or other communication link. The system can includea processor which receives information on the amount of power generatedand the amount of fuel consumed, and can thus calculate the break-evenpoint between the cost of fuel and the cost of electricity.

Alternative energy sources can also be incorporated to advantage. Forexample, solar energy can be used during periods of adequate sunlight,and gas can be used when insufficient sunlight is available. Thus energysources can include on or more of the following: waste heat, combustiongasses from burning natural gas or coal gas, electrical energy, solarenergy.

Optionally, a dew point monitor 1.027 can be connected to thecontroller. This enables the controller to determine the requiredchiller temperature or air cooling rate and the air flow rate from thefan. The dew point can be calculated by the controller from measurementsof relative humidity and temperature.

In use, the fan delivers air to the heat exchanger 1.016 at a first flowrate. The dotted line arrow 1.011 indicates the air flow through thesystem. Because this exhaust air is chilled, it can be used to delivercool, de-humidified air to a building. The absorption chiller operatesto cool the heat transfer fluid (HTF) which is delivered to the heatexchanger so that the output air from the heat exchanger is below thedew point. Where the humidity is low, the air flow rate from the fan canbe decreased. When the dew point falls below a selected threshold, thewater generating function can be discontinued by the controller. We havefound that, for a gas fired chiller, the cut-off threshold dew pointtemperature can be as low as about 0.5° C. (33° F.), while, forelectrical chillers, a cut-off dew point temperature of about 7° C. (45°F.) an be used to keep down the cost of electricity consumed.

Preferably, the cooling fins 1.018 have an upright orientation to assistthe flow of water into the collector 1.022. The fins need not bevertical, but are preferably at an angle of less than 45° to thevertical. However, they can be horizontal. The cooling fins have anenlarged area, such as extended length. Inn one embodiment, the area canbe increased by from about 10% to 100% compared with a standardrefrigeration condenser. However, larger increases are within the scopeof the invention. These fins are designed to allow the air to contactthe fins for extended time frame to allow greater extraction of vapourcombined with lower coolant temps and slower fan speeds if applicable toreach dew point.

The heat transfer fluid compressor 1.003 can be controlled on an ON/OFFmode.

The controller can be programmed to control the outlet temperature fromthe air/heat transfer fluid heat exchanger to a few degrees below thedew point to increase the rate of condensation. This temperature isreferred to as the set point.

Set point=dew point−ΔT, where ΔT is a predetermined temperature belowthe dew point.

Thus, by controlling the air flow, the temperature, the rate ofcondensation can be controlled. Optionally, the operation of thecompressor 1.003 can also be controlled to optimize the operation of thesystem. However, as compressors are designed to operate at a particularspeed, alternative methods of providing compressed HTF can be used, forexample by using two or more compressors as described below withreference to FIG. 4. The individual compressors can be switched on oroff as required to achieve the required cooling rate.

The controller can be programmed to prevent the condensate on the finsof the air/heat transfer fluid heat exchanger from freezing. However,because the air is travelling at a significant flow rate, thetemperature of the heat transfer fluid can be of the order of +5° C. to−10° C. The upper temperature can be set to below the dew point, which,in some cases can be +10° C. or higher. In one embodiment, thecontroller can be set to maintain the temperature between −5° C. and +6°C. This temperature range provides a thermal hysteresis which means thatthe gas burner can be operated intermittently rather than continuouslyif the temperature were set closer to the dew point. Thus the gas burnercan have a variable duty cycle determined by the dew point.

Preferably, the air flow in the air/heat transfer fluid heat exchangeris in a top-to-bottom direction, or at least inclined to assist thedownward flow of the water condensed from the atmosphere.

FIG. 2 illustrates a modified version of the system of FIG. 1, in whichcorresponding elements have the same item numbers as in FIG. 1.

The system of FIG. 2 includes an air/air heat exchanger 2.038 connectedby ducting 2.036 to the outlet 2.024 of the air/heat transfer fluid heatexchanger 2.016. The air flow output from the fan 2.010 is directed intothe air/air heat exchanger 2.038 and gives up heat to the cool air flowdelivered from the air/heat transfer fluid heat exchanger 2.016. Thepre-cooled air flow from the fan then enters the air/heat transfer fluidheat exchanger, and the “dehydrated” exhaust air exits via vent 2.040.This reduces the cooling work required from the chiller 2.002. Thisexhaust air is still below the ambient air temperature and can be usedto cool a building.

FIG. 3 illustrates an absorption chiller producing chilled water at3.006, returning via 3.008. The water can include an anti-freezesolution to enable it to operate at sub-zero temperatures. The workingfluid can be ammonia.

Working solution path is as follows: solution pump 3.052, rectifier3.050, pre-absorber coil 3.047, generator 3.042, at which point thelight and heavy constituents split.

The heavy constituents take a path through restrictor 3.054,pre-absorber 3.048, condenser 3.056, solution chamber 3.051.

The lighter constituents take a path through generator 3.042; rectifiertank 3.049, pre absorber 3.048, condenser 3.056 and thence to thesolution tank 3.051.

Vapour refrigerant exits the rectifier tank 3.050, to condenser 3.056,condenser restrictor 3.058, jacket of refrigerant hex 3.046, evaporatorrestrictor 3.060, evaporator 3.044 internal refrigerant heat exchanger3.045, and to the pre-absorber 3.048, where it merges with the heavierconstituents from the generator 3.042.

FIG. 4 illustrates an atmospheric water extraction system according to afurther embodiment of the invention. Specific changes in this systemcompared with the arrangement of FIG. 2 include two or more compressors4.001A and 4.001B, an additional chiller power source 4.128, togetherwith ducting 4.120, 4.124 and dampers 4.104, 4.016 adapted to use partor all of the air intake and part or all of the air outlet for airconditioning a building.

In one embodiment, the compressors can have individual air/htf heatexchangers.

The compressors are controllable so the amount of power used by thechiller operation can be varied. This is particularly useful when usingelectrical power. The system operates under the control of thecontroller 4.028. For example, in the case of a system having threecompressors, on startup of the electrical system, all the compressorsare used to bring the chiller to the set point. Then number 3 compressorcan be switched off, and if the temperature falls below the set point,number 2 compressor is switched off, leaving number 1 compressor tomaintain the temperature within a specified temperature range around theset point. The number 2 and 3 compressors can then be used as requireddepending on atmospheric conditions to maintain the system within theoperating range. Thus the higher the dew point, the less cooling energyis required.

In one embodiment, the set point can be determined in the factory, andmay be determined by the use of information relating to the localityinto which the system is to be installed. Optionally a number of setpoints can be programmed into the controller to take account of seasonalvariations.

In one embodiment, in an electrically operated mode, the set point canbe of the order of 5° C., while in the gas operated mode, the set pointcan be of the order of 0.5° C.

In a further embodiment, the controller can actively calculate the setpoint based on the prevailing atmospheric conditions, such astemperature, humidity, dew point.

When the system is powered by gas, full power is used to bring thesystem to a temperature below the set point, and the gas can then beturned off so the system uses its thermal hysteresis to continueoperating until the temperature rises to the set point, and the gas isagain applied.

The fan speed is controllable by the controller in response to theperformance of the system in the prevailing atmospheric conditions. Forexample, the fan speed can be varied in response to changes in theatmospheric dew point. Thus the optimum air flow across the air/htf heatexchanger to be maintained. If the dew point falls below a predeterminedthreshold temperature, water making is discontinued.

The controller looks at the Dew Point temp/Enthalpy/Dry Bulbtemperatures (Entering air & Leaving air) to make calculations andadjustment in fan speed. Fan speed control is based on an algorithm tomaximize dehumidification based on entering dry bulb and dew pointtemperatures. This fan speed calculates approximate tonnage to maximizeefficiency and maximize water extraction based on standard energyequation Qt=4.5 CFM (H1−H2) where H is enthalpy of entering and leavingair. The CFM is increased to keep Qt as close to maximum tonnage aschiller/absorber is capable of producing. The controller then sends anappropriate signal to Variable Frequency Drive to modify fan RPM an inturn CFM produced.

The controller can be selectively controlled by a keyboard or otherinput to operate the system in a number of different operational modes,such as water extraction only, air conditioning only, or waterextraction and air conditioning combined.

Ducting and dampers as shown in FIG. 4 can be added to control the flowof air from the system into a building. Damper 4.104 is adapted todivert air from the fan 4.010 to vent 4.122 or to an air conditioningduct 4.120. Damper 4.106 can block flow through the chiller, or divertflow from the chiller either through air/air heat exchanger 4.038 or toduct 4.124. The dampers can be controlled by the controller 4.028.

The additional power source can be, for example, electrical mains power.The controller can select the power source.

FIG. 5 is a functional block diagram of the air conditioning system of asystem according to an embodiment of the invention. The fan 5.010 drawsair through filter 5.134 and directs it to CW coil 5.136 whence itenters duct 5.120 for delivery to the air conditioned building. Exhaustvent 5.122 is controllable to divert air from the building duct whendamper 5.138 is closed. An air flow sensor 5.130 reports the air flowrate to the controller. A return duct 5.140 returns air to the inlet,controllable by damper 5.142.

FIG. 6 is a functional block diagram of the water extraction systemwhich forms part of the system of FIG. 5. The fan 6.010 filter 6.134 andCW coil 6.136 correspond to the same elements in FIG. 5. The heat pumpchiller 6.002 delivers cool water to the CW coil via pump 6.144 and thewater is then delivered to the storage tank 6.132.

FIG. 7 illustrates a controller adapted for use in an embodiment of theinvention. The controller 7.170 can be, for example, an Andover B3 851with an analog output module 7.172 and a universal input module 7.174.

A commercially available absorption chiller, such as the Robur 5 TonAbsorption Chiller, can be used to implement an embodiment of theinvention. The specification for a chiller and air handler used in anembodiment of the invention are set out below.

Specifications of the 5 Ton Gas Fired Chiller HP5T Voltage 240 V Coolingcapacity 16 kW Gas consumption @26% 67 cubic meter/hour. Total electricload (constant 540 watts. running) Weight 276 KG Dimensions 850 w × 655d× 1310 h. Noise level 49 db

Specifications of the Air Handler HP16 Kw Voltage 240 V Cooling capacity17 Kw Electrical fans (2) 240 watts and 120 watts Weight 160 KGsDimensions (horizontal) 1300 w × 600 d × 710 w Coil coated with anticorrosive coatings Filter from water collection tank to storage tank ifrequired. Circulation pump (s) ‘Manufactured water’ Transfer pump Watermanufacturing ability at 50% humidity 17 Litres/hour and 26° C.

The gas turbine can operate on natural gas, biogas, propane and othergas sources.

The system can be scaled up to provide large scale water extractioncapabilities. An air handler system capable of providing efficientcooling includes a sufficiently large fin area to ensure efficientcooling of the air below the dew point.

FIG. 8 illustrates a conventional air conditioning system 8.202 with anevaporating cooling system 8.208 to which the heat transfer fluid of theair conditioning system is connected by a hot outlet pipe 8.204 viawhich the hot fluid from the air conditioning system is delivered to thecooling tower, and a cool fluid pipe 8.206 via which the cooled fluid isreturned to the air conditioning system. The cooling system generates anoutlet of humid air due to evaporative cooling. The heat transfer fluidcan be water.

In this embodiment of the invention, the humid air discharged from thecooling tower 8.208 is harvested by a cowling 8.210 similar to a rangehood with an intake fan to draw the humid air into the cowling fromwhence it is ducted to the air intake of the condensing water generatorsuch as that described in AU2008237617. This means that the humidity ofthe air from the evaporative cooling tower 8.208 is usually higher thanambient humidity, thus the condensing water generator assists incapturing the water from the cooling tower which would otherwise be lostthrough evaporation. The water generated by the water generator can beused for a number of purposes. In one implementation, the water is fedback to replenish evaporation from the cooling tower. In an alternativesystem, the water can be used for flushing toilets.

FIG. 9 schematically illustrates an embodiment of the invention in whicha gas turbine 9.220 drives an electrical generator 9.222. Gas isdelivered to the turbine via gas supply line 9.221. The gas can benatural gas. The exhaust gasses from the turbine 9.220 are harvested bycowling 9.224 and delivered to the combined absorption chiller andcondensing water generator 9.214 as a source of heat for the absorptionchiller. Ambient air is drawn in through air inlet 9.225, using a fan asdescribed in relation to FIG. 1. The cooled air from the condensingwater generator 9.214 is delivered to an air conditioning system 9.228via duct 9.226 and hot air from the condensing water generator system islikewise delivered to the air conditioning system via duct 9.227 for usein producing conditioned (cooled/heated/dehumidified) air in thebuilding system. Manifolds, ducts and vanes can be used to control themixture of hot and cooled de-humidified air in response to anair-conditioning controller receiving information such as thetemperature of the heated and cooled air and the humidity of the cooledair and ambient humidity.

FIG. 10 schematically illustrates a system in which the capture of humidair of the arrangement of FIG. 8 is combined with the gas exhaustcapture of the arrangement of FIG. 9. This arrangement can be useful inthe case where the chiller does not produce sufficient cool air for thepurposes of the air conditioning system, so the air conditioning systemhas a second cooling source. The gas turbine 10.220 receives gas viapipe 10.221 and drives an electrical generator 10.222. The exhaust fromthe turbine is directed to the chiller 10.214, eg, via cowling andducting. The generator can be used to provide power for the fans andpumps of the system and for other on-site purposes or, where afavourable tariff arrangement is provided by the local electricityutility, to deliver power to the mains grid.

In order to reduce operating costs, the system of FIG. 10 can optionallyinclude means for incorporating one or more additional energy sourceswhich have time varying tariffs of time varying availability. Thus,advantage can be taken of, for example, low electricity tariff periods,or of availability of solar energy.

In FIG. 10, an optional mains electricity input is provided. The systemcan include a processor to select the electricity input in stead of thegas input when the cost of electricity is sufficiently low to make thisan economic choice, such as in periods of low electricity demand. Thearrangement of FIG. 10 thus includes gas meter 10.242, electricity meter10.240, mains switch 10.246, processor 10.244. The processor receivesupdated information on the electricity tariff via the internet 10.250and also receives information on the consumption of gas from gas meter10.242. The cost of gas is also accessible to the processor. Theprocessor also receives information on the amount of electricitygenerated via electricity meter 10.240. When the break-even pointbetween gas and electricity is crossed in favour of electricity, theprocessor 10.244 can turn the gas turbine off and switch the cooler10.214 to electric power.

Cool air can be diverted from duct 10.226 via duct 10.260 to cool theturbine.

Alternative sources of exhaust heat, such as reciprocating diesel orpetrol engines can be used in place of or in addition to, the turbine.

FIG. 11 is a photo-superposition illustrating the physical arrangementof a system according to an embodiment of the invention. The gas turbine11.220 drives a generator 11.222, and its exhaust gasses are directed tosupply heat to the absorption chiller 11.002 which in turn cools thewater generation heat exchanger in 11.016. Moist air from the separateair conditioning cooling tower 11.208 is harvested by the cowling 11.210and delivered to the air intake of the water generator 11.016.

The system can be modularly expandable as shown the arrangement of FIG.12, which shows an arrangement with one turbine 12.220 and 4 chillers12.002. The chillers each have a heat input connected to a hot gasmanifold 12.244 supplied via duct 12.242 from the turbine exhaust. Anumber of control vanes or valves 12.250, 12.0252, 12.254, 12.0256,12.258 control the flow of the turbine exhaust gasses inn the manifold12.244. The valve 12.250 can be used to either vent the gasses to theexterior of the manifold, or to direct the gases down the manifoldtowards the chiller inlets. The valves 12.252, 12.254, 12.256, and12.258 can be used to provide a path through the corresponding chillervia manifold outlet ducts such as 12.246.

Optionally, the chillers 12.002 can have a second heat input, such asthe gas burner input 12.260 which can be used when the turbine is notoperating. Additionally, the gas burner inputs 12.260 can be used onstart-up of the chillers, as this can require more heat than is requiredto maintain the chillers in the operational state.

Optionally, the cooled working fluid from the chillers can be can bedelivered via a working fluid circulating path including pipes 12.008,12.006 and pump 12.001 to a thermal store 12.274 which stores a largevolume of working fluid. The storage tank can be thermally insulated.The storage tank can deliver the chilled working fluid to a downstreamheat exchanger, such as 12.284, which can be part of, for example, awater maker or refrigeration system.

A controller 12.286 can be used to control the operation of the system.The controller can receive inputs from sensors such as temperaturesensor 12.276 indicating the temperature of the working fluid in thetank 12.274. The controller can then control various system parametersto ensure that the temperature of the working fluid is within apredetermined range.

Additional sensors can measure, for example, ambient temperature,relative humidity.

For example, the controller can control one or more of the following:

the operation of the chillers 12.002;

the turbine 12.220; the gas burners 12.246;

the system pumps;

the system fans.

The controller can also be responsive to information received, forexample via a communication network, such as the internet 12.300 fromone or more data sources such as server 12.032 which may containrelevant operating information, such as the relative prices ofalternative fuel sources. The information can be supplied on a pushbasis or on a pull basis.

In addition, instructions can be sent to the controller via thecommunication network from a signal originating device, shownillustratively as a computer 12.304.

The system of FIG. 12 is illustrated in the flow diagram of FIG. 13.This can be implemented using the controller 12.286. In the descriptionof the start-up routine, the chillers 12.002, 12.312, 12.314, & 12.361will be referred to as Chiller 1, Chiller 2, Chiller 3, and Chiller 4.

At step 13.402, the exhaust valve 12.250 is opened and the waste gasinlets 12.252, 12.254, 12.256, & 12.258 are closed at step 13.404.

The turbine 12.220 is then started at 13.406 and the gas burners 12.260for the Chillers 1 to 4 are turned on at step 13.408.

The temperature T_(T) of the turbine gas can then be checked at 13.410and measured against a first threshold temperature T_(op1) at 13.412 toensure the exhaust gas is at a sufficient temperature to heat theabsorption chillers. This step can generally be omitted as the exhaustgas will be above T_(op1) while the turbine is operating. If the exhaustgas is not at the operating temperature, a first delay 14.414 isinitiated during which a restart of the turbine can be attempted. If theturbine does not start after a predetermined number of attempts or apredetermined time period, an alarm can be initiated using a “watchdogtimer” or sanity check which measures the elapsed time or number ofrepeat operations of the delay loop.

A temperature measuring loop, including temperature sensing 13.416,temperature comparison 13.418, and delay 13.420, is implemented todetermine when Chiller 1 has been cooled to the chiller operatingtemperature threshold T_(op2) by the gas burner. The delay can againinclude a sanity check (time limit or repetition counter) to ensure thesystem does not become locked in a continuous loop.

When Chiller 1 has reached the operating temperature threshold T_(op2),the waste gas inlet 12.252 of Chiller 1 is opened at 13.422, the wastegas exhaust 12.250 is closed at step 13.424, and the gas burner forChiller 1 is turned off at 13.426.

Chiller 2 is next tested to determine if it has reached the operatingtemperature threshold T_(op2), again using the loop includingtemperature measurement 13.428, temperature comparison 13.430, and delay13.432. When Chiller 2 reaches the operating temperature thresholdT_(op2), the waste heat inlet 12.254 is opened at 13.434, and the gasburner for Chiller 2 is turned off at 13.436.

The process for Chillers 3 & 4 is the same as for Chiller 2 with thecorresponding waste gas inlets and burners being substituted.

Once the system has all chillers running on the waste gas from theturbine 12,220, the system then switches to monitor mode, in which itresponds to the inputs from sensors such as temperature sensor 12.276 inthe chilled working fluid reservoir 12.274.

In addition, in the monitor mode, the controller can monitor theoperation of the turbine, and, when the turbine ceases to operate, thecontroller can reignite the gas burners to run the chillers.

The arrangement of FIG. 12 can be used to bring the system rapidly tothe operating state because the gas burner can deliver greater heat thanthe exhaust gas.

FIG. 14 illustrates a general purpose chiller arrangement according toan embodiment of the invention. The absorption chiller 14.002 has a pairof heat inputs. The heat inputs can be, for example, a gas input14.004.1 and a waste heat input 14.004.2. The compressor 14.001circulates the chillers cooled working fluid from choke 14.005 betweenthe chiller and an insulated working fluid reservoir 14.274 via pipes14.006, 14.008. A temperature sensor 14.276 measures the temperature ofthe working fluid in the reservoir, and feeds this information to thecontroller 14.028. An external thermal load is supplied from thereservoir via outlet pipe 14.273 and inlet pipe 14.271. Thus, thereservoir can absorb a certain amount of heat from the external thermalload without the need for the chiller to operate continuously.

Various forms of load can be connected to the reservoir 14.274. The loadcan be an air conditioning system, a containerized data centre coolingsystem, an atmospheric water maker.

The dehumidified cooled air from the system can also be used for airconditioning purposes.

FIG. 15 illustrates a system according to a further embodiment of theinvention which uses a gas turbine electric generator to power anelectric chiller 15.462. The turbine 15.220 powers en electric generator15.222. The electricity from the generator is used to power the electricchiller 15.462 to provide chilled working fluid for the reservoir15.274.

The exhaust gasses from the turbine are used in a heat exchanger inwater heater 15.450 to heat water to provide a source of hot water.

The system can also deliver hot water using a hot water take-off pointbefore the cooling tower.

Where ever it is used, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise”, “comprised” and “comprises” where they appear.

It will be understood that the invention disclosed and defined hereinextends to all alternative combinations of two or more of the individualfeatures mentioned or evident from the text. All of these differentcombinations constitute various alternative aspects of the invention.

While particular embodiments of this invention have been described, itwill be evident to those skilled in the art that the present inventionmay be embodied in other specific forms without departing from theessential characteristics thereof. The present embodiments and examplesare therefore to be considered in all respects as illustrative and notrestrictive, and all modifications which would be obvious to thoseskilled in the art are therefore intended to be embraced therein.

1. A water extraction system having a cooling system adapted to cool airto below the dew point, the cooling system including an absorptionchiller system including a heat source, the system including an air/heattransfer fluid heat exchanger, a water collector arranged to collectwater from the air/heat transfer fluid heat exchanger, and an exothermalenergy source, wherein the cooling system is an absorption chiller, andwherein waste heat from the energy source are used as the heat source tosupply heat energy to the chiller.
 2. A water extraction system asclaimed in claim 1, including an air conditioning system using dischargeair from the water generator to control the temperature and/or humidityof the air in an air conditioned space.
 3. A water extraction system asclaimed in claim 1, including an electrical generator driven by the gasturbine.
 4. A water extraction system as claimed in claim 1, includingan air intake located to draw air from a source of humid air.
 5. A waterextraction system as claimed in claim 4, wherein the source of humid airis a cooling tower.
 6. A system as claimed in claim 5, wherein waterfrom the water extractor is fed back to the source of humid air.
 7. Awater extraction system as claimed in claim 1, including an air flowgenerator adapted to cause air to flow through the air/heat transferfluid heat exchanger.
 8. A water extraction system as claimed in claim7, wherein the air flow generator is controllable to control the airflow through the heat exchanger.
 9. A water extraction system as claimedin claim 1, wherein the heat exchanger includes a coolant pipe andcooling fins thermally connected the coolant pipe, wherein the surfacearea of the fins is enlarged to increase the time the contact surfacebetween the air flow and the fins.
 10. A water extraction system asclaimed in claim 1, including a dew point sensor to determine the dewpoint of the air.
 11. A water extraction system as claimed in claim 1,including a controller controlling the air flow generator to maintainthe temperature of the air from the heat exchanger below the dew point.12. A water extraction system as claimed in claim 8, wherein, in use,the controller is adapted to control the heat source to maintain theoutlet temperature of the heat exchanger below the dew point.
 13. Awater extraction system as claimed in claim 1, including an additionalchipper power supply.
 14. A water extraction system as claimed in claim12, wherein the additional power source is an electrical power supply.15. A water extraction system as claimed in claim 1, wherein the chillersystem includes two or more selectively switchable compressors. 16.(canceled)
 17. An absorption chiller system including two or moreabsorption chillers, each chiller having at least a first and a secondheat input, the system including a controller, wherein, on start-up ofthe chiller, the controller is adapted to turn the first heat source onto bring the chiller to a first predetermined temperature, and whereincontroller is adapted to turn the second heat source on and to turn thefirst heat source off when the corresponding chiller reaches thepredetermined temperature.
 18. A system as claimed in claim 17, whereinthe controller is adapted to bring each chiller to the predeterminedtemperature in sequence.
 19. A system as claimed in claim 17, includinga working fluid reservoir connected to store cooled working fluid fromthe chillers and to provide a thermal buffer between the chillers and athermal load.
 20. A method of extraction water from air, the methodincluding delivering hot exhaust gasses from a gas turbine to anabsorption chiller to cool an air/heat transfer fluid heat exchanger toa temperature below the dew point, and collecting water from theair/heat transfer fluid heat exchanger.
 21. A method as claimed in claim20, including the steps of: using the gas turbine to drive an electricalgenerator; and using the outlet air from the water generator to aircondition a space.
 22. (canceled)